1. Field of the Invention
The present invention relates to an indicating device for a storage battery and more particularly it related to an indicating device for indicating concentration which is installed in order to monitor the concentration of the electrolyte in a storage battery.
2. Description of the Prior Art
The amount of electrolyte in a storage battery should be kept constant. More particularly, too large an amount causes leakage, while, conversely, too small an amount results in the active substances of the electrode plates being changed into lead sulfate in the case of a lead storage battery, thus stopping the function of the storage battery. Further, even if the amount is proper, it is impossible to improve the performance of the storage battery unless the concentration (or specific gravity) of the liquid is proper.
In order to indicate the amount of electrolyte, it has been a usual practice to prepare a transparent bar-like (or pipe-like) body of methacrylic resin or styrol resin, with one end thereof pointed and inserted in the electrolyte and the other end exposed to the cover of the storage battery. This makes use of the optical property of the bar-like body such that when the pointed end of the bar-like body does not reach the electrolyte surface the bar-like body will shine white owing to total reflection as it receives the light from outside the storage battery but when it is immersed in the electrolyte, total reflection is prevented only over the immersed portion while the light-shielded interior of the electrolytic vessel is seen through and looks dark. More particularly, the dark-looking portion changes with cross-sectional shape of the bar-like body on the level of the electrolyte surface. Therefore, when the amount of electrolyte is too small, the entire area looks white, while as said amount increases, the area of the dark-looking region increases until the entire area looks dark.
On the other hand, in order to indicate the concentration of the electrolyte, it is expressed in terms of specific gravity. Therefore, specific gravity or concentration is determined by sinking and floating of a member having a predetermined specific gravity (e.g. a gravimeter).
The specific gravity of the electrolyte is correlated with the voltage of the storage battery and it has heretofore been practiced to measure the specific gravity in order to monitor the discharging and charging of the storage battery. Thus, the measurement of specific gravity is significant in order to detect over charging and completion of charging of the storage battery.